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Chanez-Paredes SD, Abtahi S, Zha J, Li E, Marsischky G, Zuo L, Grey MJ, He W, Turner JR. Mechanisms underlying distinct subcellular localization and regulation of epithelial long myosin light-chain kinase splice variants. J Biol Chem 2024; 300:105643. [PMID: 38199574 PMCID: PMC10862019 DOI: 10.1016/j.jbc.2024.105643] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2023] [Revised: 12/13/2023] [Accepted: 01/02/2024] [Indexed: 01/12/2024] Open
Abstract
Intestinal epithelia express two long myosin light-chain kinase (MLCK) splice variants, MLCK1 and MLCK2, which differ by the absence of a complete immunoglobulin (Ig)-like domain 3 within MLCK2. MLCK1 is preferentially associated with the perijunctional actomyosin ring at steady state, and this localization is enhanced by inflammatory stimuli including tumor necrosis factor (TNF). Here, we sought to identify MLCK1 domains that direct perijunctional MLCK1 localization and their relevance to disease. Ileal biopsies from Crohn's disease patients demonstrated preferential increases in MLCK1 expression and perijunctional localization relative to healthy controls. In contrast to MLCK1, MLCK2 expressed in intestinal epithelia is predominantly associated with basal stress fibers, and the two isoforms have distinct effects on epithelial migration and barrier regulation. MLCK1(Ig1-4) and MLCK1(Ig1-3), but not MLCK2(Ig1-4) or MLCK1(Ig3), directly bind to F-actin in vitro and direct perijunctional recruitment in intestinal epithelial cells. Further study showed that Ig1 is unnecessary, but that, like Ig3, the unstructured linker between Ig1 and Ig2 (Ig1/2us) is essential for recruitment. Despite being unable to bind F-actin or direct recruitment independently, Ig3 does have dominant negative functions that allow it to displace perijunctional MLCK1, increase steady-state barrier function, prevent TNF-induced MLCK1 recruitment, and attenuate TNF-induced barrier loss. These data define the minimal domain required for MLCK1 localization and provide mechanistic insight into the MLCK1 recruitment process. Overall, the results create a foundation for development of molecularly targeted therapies that target key domains to prevent MLCK1 recruitment, restore barrier function, and limit inflammatory bowel disease progression.
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Affiliation(s)
- Sandra D Chanez-Paredes
- Laboratory of Mucosal Barrier Pathobiology, Department of Pathology, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA
| | - Shabnam Abtahi
- Laboratory of Mucosal Barrier Pathobiology, Department of Pathology, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA
| | - Juanmin Zha
- Department of Oncology, The First Affiliated Hospital of Soochow University, Jiangsu Key Laboratory of Neuropsychiatric Diseases and Cambridge-Suda (CAM-SU) Genomic Resource Center, Suzhou Medical School of Soochow University, Suzhou, China
| | - Enkai Li
- Laboratory of Mucosal Barrier Pathobiology, Department of Pathology, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA
| | - Gerald Marsischky
- Laboratory of Mucosal Barrier Pathobiology, Department of Pathology, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA
| | - Li Zuo
- Laboratory of Mucosal Barrier Pathobiology, Department of Pathology, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA; Laboratory of Molecular Biology and Department of Biochemistry, Anhui Medical University, Hefei, Anhui, China
| | - Michael J Grey
- Gastroenterology Division, Department of Medicine, Beth-Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, USA
| | - Weiqi He
- Department of Oncology, The First Affiliated Hospital of Soochow University, Jiangsu Key Laboratory of Neuropsychiatric Diseases and Cambridge-Suda (CAM-SU) Genomic Resource Center, Suzhou Medical School of Soochow University, Suzhou, China.
| | - Jerrold R Turner
- Laboratory of Mucosal Barrier Pathobiology, Department of Pathology, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA.
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2
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Sorensen DW, Injeti ER, Mejia-Aguilar L, Williams JM, Pearce WJ. Postnatal development alters functional compartmentalization of myosin light chain kinase in ovine carotid arteries. Am J Physiol Regul Integr Comp Physiol 2021; 321:R441-R453. [PMID: 34318702 PMCID: PMC8530762 DOI: 10.1152/ajpregu.00293.2020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The rate-limiting enzyme for vascular contraction, myosin light chain kinase (MLCK), phosphorylates regulatory myosin light chain (MLC20) at rates that appear faster despite lower MLCK abundance in fetal compared with adult arteries. This study explores the hypothesis that greater apparent tissue activity of MLCK in fetal arteries is due to age-dependent differences in intracellular distribution of MLCK in relation to MLC20. Under optimal conditions, common carotid artery homogenates from nonpregnant adult female sheep and near-term fetuses exhibited similar values of Vmax and Km for MLCK. A custom-designed, computer-controlled apparatus enabled electrical stimulation and high-speed freezing of arterial segments at exactly 0, 1, 2, and 3 s, calculation of in situ rates of MLC20 phosphorylation, and measurement of time-dependent colocalization between MLCK and MLC20. The in situ rate of MLC20 phosphorylation divided by total MLCK abundance averaged to values 147% greater in fetal (1.06 ± 0.28) than adult (0.43 ± 0.08) arteries, which corresponded, respectively, to 43 ± 10% and 31 ± 3% of the Vmax values measured in homogenates. Confocal colocalization analysis revealed in fetal and adult arteries that 33 ± 6% and 20 ± 5% of total MLCK colocalized with pMLC20, and that MLCK activation was greater in periluminal than periadventitial regions over the time course of electrical stimulation in both age groups. Together, these results demonstrate that the catalytic activity of MLCK is similar in fetal and adult arteries, but that the fraction of total MLCK in the functional compartment involved in contraction is significantly greater in fetal than adult arteries.
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Affiliation(s)
- Dane W Sorensen
- Division of Physiology, Center for Perinatal Biology, Loma Linda University School of Medicine, Loma Linda, California
| | - Elisha R Injeti
- Department of Pharmaceutical Sciences, Cedarville University School of Pharmacy, Cedarville, Ohio
| | - Luisa Mejia-Aguilar
- Division of Physiology, Center for Perinatal Biology, Loma Linda University School of Medicine, Loma Linda, California
| | - James M Williams
- Division of Physiology, Center for Perinatal Biology, Loma Linda University School of Medicine, Loma Linda, California
| | - William J Pearce
- Division of Physiology, Center for Perinatal Biology, Loma Linda University School of Medicine, Loma Linda, California
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3
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Khapchaev AY, Watterson DM, Shirinsky VP. Phosphorylation-dependent subcellular redistribution of small myosin light chain kinase. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2021; 1868:119104. [PMID: 34302892 DOI: 10.1016/j.bbamcr.2021.119104] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Revised: 07/16/2021] [Accepted: 07/19/2021] [Indexed: 11/18/2022]
Abstract
BACKGROUND Myosin light chain kinase (MLCK) is a Ca2+-calmodulin-dependent enzyme dedicated to phosphorylate and activate myosin II to provide force for various motile processes. In smooth muscle cells and many other cells, small MLCK (S-MLCK) is a major isoform. S-MLCK is an actomyosin-binding protein firmly attached to contractile machinery in smooth muscle cells. Still, it can leave this location and contribute to other cellular processes. However, molecular mechanisms for switching the S-MLCK subcellular localization have not been described. METHODS Site-directed mutagenesis and in vitro protein phosphorylation were used to study functional roles of discrete in-vivo phosphorylated residues within the S-MLCK actin-binding domain. In vitro co-sedimentation analysis was applied to study the interaction of recombinant S-MLCK actin-binding fragment with filamentous actin. Subcellular distribution of phosphomimicking S-MLCK mutants was studied by fluorescent microscopy and differential cell extraction. RESULTS Phosphorylation of S-MLCK actin-binding domain at Ser25 and/or Thr56 by proline-directed protein kinases or phosphomimicking these posttranslational modifications alters S-MLCK binding to actin filaments both in vitro and in cells, and induces S-MLCK subcellular translocation with no effect on the enzyme catalytic properties. CONCLUSIONS Phosphorylation of the amino terminal actin-binding domain of S-MLCK renders differential subcellular targeting of the enzyme and may, thereby, contribute to a variety of context-dependent responses of S-MLCK to cellular and tissue stimuli. GENERAL SIGNIFICANCE S-MLCK physiological function can potentially be modulated via phosphorylation of its actin recognition domain, a regulation distinct from the catalytic and calmodulin regulatory domains.
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Affiliation(s)
- Asker Y Khapchaev
- National Medical Research Center for Cardiology, 3rd Cherepkovskaya St., 15a, Moscow 121552, Russian Federation.
| | | | - Vladimir P Shirinsky
- National Medical Research Center for Cardiology, 3rd Cherepkovskaya St., 15a, Moscow 121552, Russian Federation
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4
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Magliozzi JO, Moseley JB. Connecting cell polarity signals to the cytokinetic machinery in yeast and metazoan cells. Cell Cycle 2021; 20:1-10. [PMID: 33397181 DOI: 10.1080/15384101.2020.1864941] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
Abstract
Polarized growth and cytokinesis are two fundamental cellular processes that exist in virtually all cell types. Mechanisms for asymmetric distribution of materials allow for cells to grow in a polarized manner. This gives rise to a variety of cell shapes seen throughout all cell types. Following polarized growth during interphase, dividing cells assemble a cytokinetic ring containing the protein machinery to constrict and separate daughter cells. Here, we discuss how cell polarity signaling pathways act on cytokinesis, with a focus on direct regulation of the contractile actomyosin ring (CAR). Recent studies have exploited phosphoproteomics to identify new connections between cell polarity kinases and CAR proteins. Existing evidence suggests that some polarity kinases guide the local organization of CAR proteins and structures while also contributing to global organization of the division plane within a cell. We provide several examples of this regulation from budding yeast, fission yeast, and metazoan cells. In some cases, kinase-substrate connections point to conserved processes in these different organisms. We point to several examples where future work can indicate the degree of conservation and divergence in the cell division process of these different organisms.
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Affiliation(s)
- Joseph O Magliozzi
- Department of Biochemistry and Cell Biology, The Geisel School of Medicine at Dartmouth , Hanover, New Hampshire, USA
| | - James B Moseley
- Department of Biochemistry and Cell Biology, The Geisel School of Medicine at Dartmouth , Hanover, New Hampshire, USA
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5
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X Cai L, Tanada Y, D Bello G, C Fleming J, F Alkassis F, Ladd T, Golde T, Koh J, Chen S, Kasahara H. Cardiac MLC2 kinase is localized to the Z-disc and interacts with α-actinin2. Sci Rep 2019; 9:12580. [PMID: 31467300 PMCID: PMC6715661 DOI: 10.1038/s41598-019-48884-w] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2019] [Accepted: 08/13/2019] [Indexed: 02/07/2023] Open
Abstract
Cardiac contractility is enhanced by phosphorylation of myosin light chain 2 (MLC2) by cardiac-specific MLC kinase (cMLCK), located at the neck region of myosin heavy chain. In normal mouse and human hearts, the level of phosphorylation is maintained relatively constant, at around 30-40% of total MLC2, likely by well-balanced phosphorylation and phosphatase-dependent dephosphorylation. Overexpression of cMLCK promotes sarcomere organization, while the loss of cMLCK leads to cardiac atrophy in vitro and in vivo. In this study, we showed that cMLCK is predominantly expressed at the Z-disc with additional diffuse cytosolic expression in normal adult mouse and human hearts. cMLCK interacts with the Z-disc protein, α-actinin2, with a high-affinity kinetic value of 13.4 ± 0.1 nM through the N-terminus region of cMLCK unique to cardiac-isoform. cMLCK mutant deficient for interacting with α-actinin2 did not promote sarcomeric organization and reduced cardiomyocyte cell size. In contrast, a cMLCK kinase-deficient mutant showed effects similar to wild-type cMLCK on sarcomeric organization and cardiomyocyte cell size. Our results suggest that cMLCK plays a role in sarcomere organization, likely distinct from its role in phosphorylating MLC2, both of which will contribute to the enhancement of cardiac contractility.
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Affiliation(s)
- Lawrence X Cai
- Department of Physiology and Functional Genomics, University of Florida, College of Medicine, Gainesville, FL, 32610, USA
| | - Yohei Tanada
- Department of Physiology and Functional Genomics, University of Florida, College of Medicine, Gainesville, FL, 32610, USA
| | - Gregory D Bello
- Department of Physiology and Functional Genomics, University of Florida, College of Medicine, Gainesville, FL, 32610, USA
| | - James C Fleming
- Department of Physiology and Functional Genomics, University of Florida, College of Medicine, Gainesville, FL, 32610, USA
| | - Fariz F Alkassis
- Department of Physiology and Functional Genomics, University of Florida, College of Medicine, Gainesville, FL, 32610, USA
| | - Thomas Ladd
- Department of Neuroscience, University of Florida, College of Medicine, Gainesville, FL, 32610, USA
| | - Todd Golde
- Department of Neuroscience, University of Florida, College of Medicine, Gainesville, FL, 32610, USA
| | - Jin Koh
- Proteomics and Mass Spectrometry, Interdisciplinary Center for Biotechnology Research (ICBR), University of Florida, Gainesville, FL, 32610, USA
| | - Sixue Chen
- Proteomics and Mass Spectrometry, Interdisciplinary Center for Biotechnology Research (ICBR), University of Florida, Gainesville, FL, 32610, USA.,Department of Biology, Genetics Institute, Plant Molecular and Cellular Biology Program, University of Florida, Gainesville, FL, 32610, USA
| | - Hideko Kasahara
- Department of Physiology and Functional Genomics, University of Florida, College of Medicine, Gainesville, FL, 32610, USA.
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6
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Wang Q, Qian W, Xu X, Bajpai A, Guan K, Zhang Z, Chen R, Flamini V, Chen W. Energy-Mediated Machinery Drives Cellular Mechanical Allostasis. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2019; 31:e1900453. [PMID: 31270881 PMCID: PMC11157583 DOI: 10.1002/adma.201900453] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2019] [Revised: 06/06/2019] [Indexed: 06/09/2023]
Abstract
Allostasis is a fundamental biological process through which living organisms achieve stability via physiological or behavioral changes to protect against internal and external stresses, and ultimately better adapt to the local environment. However, an full understanding of cellular-level allostasis is far from developed. By employing an integrated micromechanical tool capable of applying controlled mechanical stress on an individual cell and simultaneously reporting dynamic information of subcellular mechanics, individual cell allostasis is observed to occur through a biphasic process; cellular mechanics tends to restore to a stable state through a mechanoadaptative process with excitative biophysical activity followed by a decaying adaptive phase. Based on these observations, it is found that cellular allostasis occurs through a complex balance of subcellular energy and cellular mechanics; upon a transient and local physical stimulation, cells trigger an allostatic state that maximizes energy and overcomes a mechanical "energy barrier" followed by a relaxation state that reaches its mechanobiological stabilization and energy minimization. Discoveries of energy-driven cellular machinery and conserved mechanotransductive pathways underscore the critical role of force-sensitive cytoskeleton equilibrium in cellular allostasis. This highlight the biophysical origin of cellular mechanical allostasis, providing subcellular methods to understand the etiology and progression of certain diseases or aging.
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Affiliation(s)
- Qianbin Wang
- Department of Mechanical and Aerospace Engineering, New York University, Brooklyn, NY, 11201, USA
| | - Weiyi Qian
- Department of Mechanical and Aerospace Engineering, New York University, Brooklyn, NY, 11201, USA
| | - Xiaoyu Xu
- Department of Mechanical and Aerospace Engineering, New York University, Brooklyn, NY, 11201, USA
| | - Apratim Bajpai
- Department of Mechanical and Aerospace Engineering, New York University, Brooklyn, NY, 11201, USA
| | - Kevin Guan
- Department of Mechanical and Aerospace Engineering, New York University, Brooklyn, NY, 11201, USA
| | - Zijing Zhang
- Department of Mechanical and Aerospace Engineering, New York University, Brooklyn, NY, 11201, USA
| | - Roy Chen
- Department of Mechanical and Aerospace Engineering, New York University, Brooklyn, NY, 11201, USA
| | - Vittoria Flamini
- Department of Mechanical and Aerospace Engineering, New York University, Brooklyn, NY, 11201, USA
| | - Weiqiang Chen
- Department of Mechanical and Aerospace Engineering, New York University, Brooklyn, NY, 11201, USA
- Department of Biomedical Engineering, New York University, Brooklyn, NY, 11201, USA
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7
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Iguchi N, Dönmez Mİ, Carrasco A, Wilcox DT, Pineda RH, Malykhina AP, Cost NG. Doxorubicin induces detrusor smooth muscle impairments through myosin dysregulation, leading to a risk of lower urinary tract dysfunction. Am J Physiol Renal Physiol 2019; 317:F197-F206. [PMID: 31066574 DOI: 10.1152/ajprenal.00090.2019] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Cytotoxic chemotherapy is the foundation for the treatment of the wide variety of childhood malignancies; however, these therapies are known to have a variety of deleterious side effects. One common chemotherapy used in children, doxorubicin (DOX), is well known to cause cardiotoxicity and cardiomyopathy. Recent studies have revealed that DOX impairs skeletal and smooth muscle function and contributes to fatigue and abnormal intestinal motility in patients. In this study, we tested the hypothesis that systemic DOX administration also affects detrusor smooth muscle (DSM) function in the urinary bladder, especially when administered at a young age. The effects on the DSM and bladder function were assessed in BALB/cJ mice that received six weekly intravenous injections of DOX (3 mg·kg-1·wk-1) or saline for the control group. Systemic DOX administration resulted in DSM hypertrophy, increased voiding frequency, and a significant attenuation of DSM contractility, followed by a slower relaxation compared with the control group. Gene expression analyses revealed that unlike DOX-induced cardiotoxicity, the bladders from DOX-administered animals showed no changes in oxidative stress markers; instead, downregulation of large-conductance Ca2+-activated K+ channels and altered expression of myosin light-chain kinase coincided with reduced myosin light-chain phosphorylation. These results indicate that in vivo DOX exposure caused DSM dysfunction by dysregulation of molecules involved in the detrusor contractile-relaxation mechanisms. Collectively, our findings suggest that survivors of childhood cancer treated with DOX may be at increased risk of bladder dysfunction and benefit from followup surveillance of bladder function.
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Affiliation(s)
- Nao Iguchi
- Division of Urology, Department of Surgery, University of Colorado Denver School of Medicine , Aurora, Colorado
| | - M İrfan Dönmez
- Division of Urology, Department of Surgery, University of Colorado Denver School of Medicine , Aurora, Colorado.,Children's Hospital Colorado , Aurora, Colorado
| | - Alonso Carrasco
- Children's Hospital Colorado , Aurora, Colorado.,Children's Mercy Kansas City, Kansas City, Missouri
| | - Duncan T Wilcox
- Division of Urology, Department of Surgery, University of Colorado Denver School of Medicine , Aurora, Colorado.,Children's Hospital Colorado , Aurora, Colorado
| | - Ricardo H Pineda
- Division of Urology, Department of Surgery, University of Colorado Denver School of Medicine , Aurora, Colorado
| | - Anna P Malykhina
- Division of Urology, Department of Surgery, University of Colorado Denver School of Medicine , Aurora, Colorado
| | - Nicholas G Cost
- Division of Urology, Department of Surgery, University of Colorado Denver School of Medicine , Aurora, Colorado.,Children's Hospital Colorado , Aurora, Colorado
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8
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Schneidewind T, Kapoor S, Garivet G, Karageorgis G, Narayan R, Vendrell-Navarro G, Antonchick AP, Ziegler S, Waldmann H. The Pseudo Natural Product Myokinasib Is a Myosin Light Chain Kinase 1 Inhibitor with Unprecedented Chemotype. Cell Chem Biol 2019; 26:512-523.e5. [DOI: 10.1016/j.chembiol.2018.11.014] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2016] [Revised: 09/14/2018] [Accepted: 11/26/2018] [Indexed: 12/20/2022]
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9
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Wang P, Dreger M, Madrazo E, Williams CJ, Samaniego R, Hodson NW, Monroy F, Baena E, Sánchez-Mateos P, Hurlstone A, Redondo-Muñoz J. WDR5 modulates cell motility and morphology and controls nuclear changes induced by a 3D environment. Proc Natl Acad Sci U S A 2018; 115:8581-8586. [PMID: 29987046 PMCID: PMC6112728 DOI: 10.1073/pnas.1719405115] [Citation(s) in RCA: 60] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Cell migration through extracellular matrices requires nuclear deformation, which depends on nuclear stiffness. In turn, chromatin structure contributes to nuclear stiffness, but the mechanosensing pathways regulating chromatin during cell migration remain unclear. Here, we demonstrate that WD repeat domain 5 (WDR5), an essential component of H3K4 methyltransferase complexes, regulates cell polarity, nuclear deformability, and migration of lymphocytes in vitro and in vivo, independent of transcriptional activity, suggesting nongenomic functions for WDR5. Similarly, depletion of RbBP5 (another H3K4 methyltransferase subunit) promotes similar defects. We reveal that a 3D environment increases the H3K4 methylation dependent on WDR5 and results in a globally less compacted chromatin conformation. Further, using atomic force microscopy, nuclear particle tracking, and nuclear swelling experiments, we detect changes in nuclear mechanics that accompany the epigenetic changes induced in 3D conditions. Indeed, nuclei from cells in 3D environments were softer, and thereby more deformable, compared with cells in suspension or cultured in 2D conditions, again dependent on WDR5. Dissecting the underlying mechanism, we determined that actomyosin contractility, through the phosphorylation of myosin by MLCK (myosin light chain kinase), controls the interaction of WDR5 with other components of the methyltransferase complex, which in turn up-regulates H3K4 methylation activation in 3D conditions. Taken together, our findings reveal a nongenomic function for WDR5 in regulating H3K4 methylation induced by 3D environments, physical properties of the nucleus, cell polarity, and cell migratory capacity.
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Affiliation(s)
- Pengbo Wang
- Wellcome Trust Centre for Cell-Matrix Research, Faculty of Biology, Medicine and Health, School of Medical Sciences, Division of Cell Matrix Biology and Regenerative Medicine, The University of Manchester, M13 9PT Manchester, United Kingdom
- Prostate Oncobiology Group, Cancer Research UK Manchester Institute, SK10 4TG Manchester, United Kingdom
| | - Marcel Dreger
- Faculty of Biology, Medicine and Health, Division of Cancer Sciences, School of Medical Sciences, The University of Manchester, M13 9PT Manchester, United Kingdom
| | - Elena Madrazo
- Section of Immuno-oncology, Instituto de Investigación Sanitaria Gregorio Marañón, Complutense University, School of Medicine, 28007 Madrid, Spain
- Department of Immunology, Hospital 12 de Octubre Health Research Institute (imas12), Complutense University, School of Medicine, 28040 Madrid, Spain
| | - Craig J Williams
- School of Materials, The University of Manchester, M13 9PL Manchester, United Kingdom
| | - Rafael Samaniego
- Confocal Microscopy Unit, Instituto de Investigación Sanitaria Gregorio Marañón, 28007 Madrid, Spain
| | - Nigel W Hodson
- BioAFM Facility, The University of Manchester, M13 9PG Manchester, United Kingdom
| | - Francisco Monroy
- Department of Physical Chemistry, Hospital 12 de Octubre Health Research Institute (imas12), Complutense University, 28040 Madrid, Spain
| | - Esther Baena
- Prostate Oncobiology Group, Cancer Research UK Manchester Institute, SK10 4TG Manchester, United Kingdom
| | - Paloma Sánchez-Mateos
- Section of Immuno-oncology, Instituto de Investigación Sanitaria Gregorio Marañón, Complutense University, School of Medicine, 28007 Madrid, Spain
| | - Adam Hurlstone
- Faculty of Biology, Medicine and Health, Division of Cancer Sciences, School of Medical Sciences, The University of Manchester, M13 9PT Manchester, United Kingdom
| | - Javier Redondo-Muñoz
- Department of Immunology, Hospital 12 de Octubre Health Research Institute (imas12), Complutense University, School of Medicine, 28040 Madrid, Spain;
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10
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Kelley CA, Wirshing ACE, Zaidel-Bar R, Cram EJ. The myosin light-chain kinase MLCK-1 relocalizes during Caenorhabditis elegans ovulation to promote actomyosin bundle assembly and drive contraction. Mol Biol Cell 2018; 29:1975-1991. [PMID: 30088798 PMCID: PMC6232974 DOI: 10.1091/mbc.e18-01-0056] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
We identify the Caenorhabditis elegans myosin light-chain kinase, MLCK-1, required for contraction of spermathecae. During contraction, MLCK-1 moves from the apical cell boundaries to the basal actomyosin bundles, where it stabilizes myosin downstream of calcium signaling. MLCK and ROCK act in distinct subsets of cells to coordinate the timing of contraction.
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Affiliation(s)
| | | | - Ronen Zaidel-Bar
- Department of Cell and Developmental Biology, Sackler School of Medicine, Tel-Aviv University, Tel-Aviv 69978, Israel
| | - Erin J Cram
- Department of Biology, Northeastern University, Boston, MA 02115
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11
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Khapchaev AY, Shirinsky VP. Myosin Light Chain Kinase MYLK1: Anatomy, Interactions, Functions, and Regulation. BIOCHEMISTRY (MOSCOW) 2017; 81:1676-1697. [PMID: 28260490 DOI: 10.1134/s000629791613006x] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
This review discusses and summarizes the results of molecular and cellular investigations of myosin light chain kinase (MLCK, MYLK1), the key regulator of cell motility. The structure and regulation of a complex mylk1 gene and the domain organization of its products is presented. The interactions of the mylk1 gene protein products with other proteins and posttranslational modifications of the mylk1 gene protein products are reviewed, which altogether might determine the role and place of MLCK in physiological and pathological reactions of cells and entire organisms. Translational potential of MLCK as a drug target is evaluated.
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Affiliation(s)
- A Y Khapchaev
- Russian Cardiology Research and Production Center, Moscow, 121552, Russia.
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12
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Pandya P, Orgaz JL, Sanz-Moreno V. Modes of invasion during tumour dissemination. Mol Oncol 2016; 11:5-27. [PMID: 28085224 PMCID: PMC5423224 DOI: 10.1002/1878-0261.12019] [Citation(s) in RCA: 116] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Revised: 10/24/2016] [Accepted: 10/28/2016] [Indexed: 02/06/2023] Open
Abstract
Cancer cell migration and invasion underlie metastatic dissemination, one of the major problems in cancer. Tumour cells exhibit a striking variety of invasion strategies. Importantly, cancer cells can switch between invasion modes in order to cope with challenging environments. This ability to switch migratory modes or plasticity highlights the challenges behind antimetastasis therapy design. In this Review, we present current knowledge on different tumour invasion strategies, the determinants controlling plasticity and arising therapeutic opportunities. We propose that targeting master regulators controlling plasticity is needed to hinder tumour dissemination and metastasis.
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Affiliation(s)
- Pahini Pandya
- Tumour Plasticity Team, Randall Division of Cell and Molecular Biophysics, King's College London, UK
| | - Jose L Orgaz
- Tumour Plasticity Team, Randall Division of Cell and Molecular Biophysics, King's College London, UK
| | - Victoria Sanz-Moreno
- Tumour Plasticity Team, Randall Division of Cell and Molecular Biophysics, King's College London, UK
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13
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Vilitkevich EL, Khapchaev AY, Kudryashov DS, Nikashin AV, Schavocky JP, Lukas TJ, Watterson DM, Shirinsky VP. Phosphorylation Regulates Interaction of 210-kDa Myosin Light Chain Kinase N-terminal Domain with Actin Cytoskeleton. BIOCHEMISTRY (MOSCOW) 2016; 80:1288-97. [PMID: 26567572 DOI: 10.1134/s0006297915100090] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
High molecular weight myosin light chain kinase (MLCK210) is a multifunctional protein involved in myosin II activation and integration of cytoskeletal components in cells. MLCK210 possesses actin-binding regions both in the central part of the molecule and in its N-terminal tail domain. In HeLa cells, mitotic protein kinase Aurora B was suggested to phosphorylate MLCK210 N-terminal tail at serine residues (Dulyaninova, N. G., and Bresnick, A. R. (2004) Exp. Cell Res., 299, 303-314), but the functional significance of the phosphorylation was not established. We report here that in vitro, the N-terminal actin-binding domain of MLCK210 is located within residues 27-157 (N27-157, avian MLCK210 sequence) and is phosphorylated by cAMP-dependent protein kinase (PKA) and Aurora B at serine residues 140/149 leading to a decrease in N27-157 binding to actin. The same residues are phosphorylated in a PKA-dependent manner in transfected HeLa cells. Further, in transfected cells, phosphomimetic mutants of N27-157 showed reduced association with the detergent-stable cytoskeleton, whereas in vitro, the single S149D mutation reduced N27-157 association with F-actin to a similar extent as that achieved by N27-157 phosphorylation. Altogether, our results indicate that phosphorylation of MLCK210 at distinct serine residues, mainly at S149, attenuates the interaction of MLCK210 N-terminus with the actin cytoskeleton and might serve to regulate MLCK210 microfilament cross-linking activity in cells.
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Affiliation(s)
- E L Vilitkevich
- Russian Cardiology Research and Production Center, Moscow, 121552, Russia.
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14
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Massengill MT, Ashraf HM, Chowdhury RR, Chrzanowski SM, Kar J, Warren SA, Walter GA, Zeng H, Kang BH, Anderson RH, Moss RL, Kasahara H. Acute heart failure with cardiomyocyte atrophy induced in adult mice by ablation of cardiac myosin light chain kinase. Cardiovasc Res 2016; 111:34-43. [PMID: 27025239 DOI: 10.1093/cvr/cvw069] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/31/2015] [Accepted: 03/17/2016] [Indexed: 12/31/2022] Open
Abstract
AIMS Under pressure overload, initial adaptive hypertrophy of the heart is followed by cardiomyocyte elongation, reduced contractile force, and failure. The mechanisms governing the transition to failure are not fully understood. Pressure overload reduced cardiac myosin light chain kinase (cMLCK) by ∼80% within 1 week and persists. Knockdown of cMLCK in cardiomyocytes resulted in reduced cardiac contractility and sarcomere disorganization. Thus, we hypothesized that acute reduction of cMLCK may be causative for reduced contractility and cardiomyocyte remodelling during the transition from compensated to decompensated cardiac hypertrophy. METHODS AND RESULTS To mimic acute cMLCK reduction in adult hearts, the floxed-Mylk3 gene that encodes cMLCK was inducibly ablated in Mylk3(flox/flox)/merCremer mice (Mylk3-KO), and compared with two control mice (Mylk3(flox/flox) and Mylk3(+/+)/merCremer) following tamoxifen injection (50 mg/kg/day, 2 consecutive days). In Mylk3-KO mice, reduction of cMLCK protein was evident by 4 days, with a decline to below the level of detection by 6 days. By 7 days, these mice exhibited heart failure, with reduction of fractional shortening compared with those in two control groups (19.8 vs. 28.0% and 27.7%). Severely convoluted cardiomyocytes with sarcomeric disorganization, wavy fibres, and cell death were demonstrated in Mylk3-KO mice. The cardiomyocytes were also unable to thicken adaptively to pressure overload. CONCLUSION Our results, using a new mouse model mimicking an acute reduction of cMLCK, suggest that cMLCK plays a pivotal role in the transition from compensated to decompensated hypertrophy via sarcomeric disorganization.
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Affiliation(s)
- Michael T Massengill
- Department of Physiology and Functional Genomics, University of Florida College of Medicine, 1600 SW Archer Rd, M543, Gainesville, FL 32610-0274, USA
| | - Hassan M Ashraf
- Department of Physiology and Functional Genomics, University of Florida College of Medicine, 1600 SW Archer Rd, M543, Gainesville, FL 32610-0274, USA
| | - Rajib R Chowdhury
- Department of Physiology and Functional Genomics, University of Florida College of Medicine, 1600 SW Archer Rd, M543, Gainesville, FL 32610-0274, USA
| | - Stephen M Chrzanowski
- Department of Physiology and Functional Genomics, University of Florida College of Medicine, 1600 SW Archer Rd, M543, Gainesville, FL 32610-0274, USA
| | - Jeena Kar
- Department of Physiology and Functional Genomics, University of Florida College of Medicine, 1600 SW Archer Rd, M543, Gainesville, FL 32610-0274, USA
| | - Sonisha A Warren
- Department of Physiology and Functional Genomics, University of Florida College of Medicine, 1600 SW Archer Rd, M543, Gainesville, FL 32610-0274, USA
| | - Glenn A Walter
- Department of Physiology and Functional Genomics, University of Florida College of Medicine, 1600 SW Archer Rd, M543, Gainesville, FL 32610-0274, USA
| | - Huadong Zeng
- Advanced Magnetic Resonance Imaging and Spectroscopy Facility, University of Florida, Gainesville, FL, USA
| | - Byung-Ho Kang
- Electron Microscopy and Bio-imaging Laboratory, University of Florida, Gainesville, FL, USA
| | | | - Richard L Moss
- Department of Cell and Regenerative Biology, University of Wisconsin School of Medicine and Public Health, Madison, WI 53706, USA
| | - Hideko Kasahara
- Department of Physiology and Functional Genomics, University of Florida College of Medicine, 1600 SW Archer Rd, M543, Gainesville, FL 32610-0274, USA
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15
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Shen K, Ramirez B, Mapes B, Shen GR, Gokhale V, Brown ME, Santarsiero B, Ishii Y, Dudek SM, Wang T, Garcia JGN. Structure-Function Analysis of the Non-Muscle Myosin Light Chain Kinase (nmMLCK) Isoform by NMR Spectroscopy and Molecular Modeling: Influence of MYLK Variants. PLoS One 2015; 10:e0130515. [PMID: 26111161 PMCID: PMC4482139 DOI: 10.1371/journal.pone.0130515] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2015] [Accepted: 05/22/2015] [Indexed: 01/29/2023] Open
Abstract
The MYLK gene encodes the multifunctional enzyme, myosin light chain kinase (MLCK), involved in isoform-specific non-muscle and smooth muscle contraction and regulation of vascular permeability during inflammation. Three MYLK SNPs (P21H, S147P, V261A) alter the N-terminal amino acid sequence of the non-muscle isoform of MLCK (nmMLCK) and are highly associated with susceptibility to acute lung injury (ALI) and asthma, especially in individuals of African descent. To understand the functional effects of SNP associations, we examined the N-terminal segments of nmMLCK by 1H-15N heteronuclear single quantum correlation (HSQC) spectroscopy, a 2-D NMR technique, and by in silico molecular modeling. Both NMR analysis and molecular modeling indicated SNP localization to loops that connect the immunoglobulin-like domains of nmMLCK, consistent with minimal structural changes evoked by these SNPs. Molecular modeling analysis identified protein-protein interaction motifs adversely affected by these MYLK SNPs including binding by the scaffold protein 14-3-3, results confirmed by immunoprecipitation and western blot studies. These structure-function studies suggest novel mechanisms for nmMLCK regulation, which may confirm MYLK as a candidate gene in inflammatory lung disease and advance knowledge of the genetic underpinning of lung-related health disparities.
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Affiliation(s)
- Kui Shen
- Institute for Personalized Respiratory Medicine, Section of Pulmonary, Critical Care, Sleep, and Allergy, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Benjamin Ramirez
- Center for Structural Biology, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Brandon Mapes
- Institute for Personalized Respiratory Medicine, Section of Pulmonary, Critical Care, Sleep, and Allergy, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Grace R. Shen
- Institute for Personalized Respiratory Medicine, Section of Pulmonary, Critical Care, Sleep, and Allergy, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Vijay Gokhale
- College of Pharmacy and BIO5 Institute, University of Arizona, Tucson, Arizona, United States of America
| | - Mary E. Brown
- Institute for Personalized Respiratory Medicine, Section of Pulmonary, Critical Care, Sleep, and Allergy, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Bernard Santarsiero
- Center for Structural Biology, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Yoshitaka Ishii
- Center for Structural Biology, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Steven M. Dudek
- Institute for Personalized Respiratory Medicine, Section of Pulmonary, Critical Care, Sleep, and Allergy, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Ting Wang
- Institute for Personalized Respiratory Medicine, Section of Pulmonary, Critical Care, Sleep, and Allergy, University of Illinois at Chicago, Chicago, Illinois, United States of America
- Arizona Respiratory Center and Department of Medicine, University of Arizona, Tucson, Arizona, United States of America
| | - Joe G. N. Garcia
- Institute for Personalized Respiratory Medicine, Section of Pulmonary, Critical Care, Sleep, and Allergy, University of Illinois at Chicago, Chicago, Illinois, United States of America
- Arizona Respiratory Center and Department of Medicine, University of Arizona, Tucson, Arizona, United States of America
- * E-mail:
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16
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Akhshi TK, Wernike D, Piekny A. Microtubules and actin crosstalk in cell migration and division. Cytoskeleton (Hoboken) 2013; 71:1-23. [DOI: 10.1002/cm.21150] [Citation(s) in RCA: 110] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2013] [Revised: 10/02/2013] [Accepted: 10/06/2013] [Indexed: 12/22/2022]
Affiliation(s)
| | - Denise Wernike
- Department of Biology; Concordia University; Montreal Quebec Canada
| | - Alisa Piekny
- Department of Biology; Concordia University; Montreal Quebec Canada
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17
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Smith TC, Fridy PC, Li Y, Basil S, Arjun S, Friesen RM, Leszyk J, Chait BT, Rout MP, Luna EJ. Supervillin binding to myosin II and synergism with anillin are required for cytokinesis. Mol Biol Cell 2013; 24:3603-19. [PMID: 24088567 PMCID: PMC3842989 DOI: 10.1091/mbc.e12-10-0714] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Cytokinesis, the process by which cytoplasm is apportioned between dividing daughter cells, requires coordination of myosin II function, membrane trafficking, and central spindle organization. Most known regulators act during late cytokinesis; a few, including the myosin II-binding proteins anillin and supervillin, act earlier. Anillin's role in scaffolding the membrane cortex with the central spindle is well established, but the mechanism of supervillin action is relatively uncharacterized. We show here that two regions within supervillin affect cell division: residues 831-1281, which bind central spindle proteins, and residues 1-170, which bind the myosin II heavy chain (MHC) and the long form of myosin light-chain kinase. MHC binding is required to rescue supervillin deficiency, and mutagenesis of this site creates a dominant-negative phenotype. Supervillin concentrates activated and total myosin II at the furrow, and simultaneous knockdown of supervillin and anillin additively increases cell division failure. Knockdown of either protein causes mislocalization of the other, and endogenous anillin increases upon supervillin knockdown. Proteomic identification of interaction partners recovered using a high-affinity green fluorescent protein nanobody suggests that supervillin and anillin regulate the myosin II and actin cortical cytoskeletons through separate pathways. We conclude that supervillin and anillin play complementary roles during vertebrate cytokinesis.
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Affiliation(s)
- Tara C Smith
- Program in Cell and Developmental Dynamics, Department of Cell and Developmental Biology, University of Massachusetts Medical School, Worcester, MA 01655 Laboratory of Cellular and Structural Biology, Rockefeller University, New York, NY 10065 Laboratory of Mass Spectrometry and Gaseous Ion Chemistry, Rockefeller University, New York, NY 10065 Proteomics and Mass Spectrometry Facility, University of Massachusetts Medical School, Shrewsbury, MA 01545
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18
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Lawrence EJ, Mandato CA. Mitochondria localize to the cleavage furrow in mammalian cytokinesis. PLoS One 2013; 8:e72886. [PMID: 23991162 PMCID: PMC3749163 DOI: 10.1371/journal.pone.0072886] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2013] [Accepted: 07/21/2013] [Indexed: 01/08/2023] Open
Abstract
Mitochondria are dynamic organelles with multiple cellular functions, including ATP production, calcium buffering, and lipid biosynthesis. Several studies have shown that mitochondrial positioning is regulated by the cytoskeleton during cell division in several eukaryotic systems. However, the distribution of mitochondria during mammalian cytokinesis and whether the distribution is regulated by the cytoskeleton has not been examined. Using live spinning disk confocal microscopy and quantitative analysis of mitochondrial fluorescence intensity, we demonstrate that mitochondria are recruited to the cleavage furrow during cytokinesis in HeLa cells. After anaphase onset, the mitochondria are recruited towards the site of cleavage furrow formation, where they remain enriched as the furrow ingresses and until cytokinesis completion. Furthermore, we show that recruitment of mitochondria to the furrow occurs in multiple mammalian cells lines as well as in monopolar, bipolar, and multipolar divisions, suggesting that the mechanism of recruitment is conserved and robust. Using inhibitors of cytoskeleton dynamics, we show that the microtubule cytoskeleton, but not actin, is required to transport mitochondria to the cleavage furrow. Thus, mitochondria are specifically recruited to the cleavage furrow in a microtubule-dependent manner during mammalian cytokinesis. Two possible reasons for this could be to localize mitochondrial function to the furrow to facilitate cytokinesis and / or ensure accurate mitochondrial inheritance.
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Affiliation(s)
| | - Craig A. Mandato
- Department of Anatomy and Cell Biology, McGill University, Montreal, Quebec, Canada
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19
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Kondo T, Isoda R, Ookusa T, Kamijo K, Hamao K, Hosoya H. Aurora B but not rho/MLCK signaling is required for localization of diphosphorylated myosin II regulatory light chain to the midzone in cytokinesis. PLoS One 2013; 8:e70965. [PMID: 23951055 PMCID: PMC3737224 DOI: 10.1371/journal.pone.0070965] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2012] [Accepted: 06/25/2013] [Indexed: 01/21/2023] Open
Abstract
Non-muscle myosin II is stimulated by monophosphorylation of its regulatory light chain (MRLC) at Ser19 (1P-MRLC). MRLC diphosphorylation at Thr18/Ser19 (2P-MRLC) further enhances the ATPase activity of myosin II. Phosphorylated MRLCs localize to the contractile ring and regulate cytokinesis as subunits of activated myosin II. Recently, we reported that 2P-MRLC, but not 1P-MRLC, localizes to the midzone independently of myosin II heavy chain during cytokinesis in cultured mammalian cells. However, the mechanism underlying the distinct localization of 1P- and 2P-MRLC during cytokinesis is unknown. Here, we showed that depletion of the Rho signaling proteins MKLP1, MgcRacGAP, or ECT2 inhibited the localization of 1P-MRLC to the contractile ring but not the localization of 2P-MRLC to the midzone. In contrast, depleting or inhibiting a midzone-localizing kinase, Aurora B, perturbed the localization of 2P-MRLC to the midzone but not the localization of 1P-MRLC to the contractile ring. We did not observe any change in the localization of phosphorylated MRLC in myosin light-chain kinase (MLCK)-inhibited cells. Furrow regression was observed in Aurora B- and 2P-MRLC-inhibited cells but not in 1P-MRLC-perturbed dividing cells. Furthermore, Aurora B bound to 2P-MRLC in vitro and in vivo. These results suggest that Aurora B, but not Rho/MLCK signaling, is essential for the localization of 2P-MRLC to the midzone in dividing HeLa cells.
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Affiliation(s)
- Tomo Kondo
- Department of Biological Science, Graduate School of Science, Hiroshima University, Higashi-Hiroshima, Hiroshima, Japan
| | - Rieko Isoda
- Department of Biological Science, Graduate School of Science, Hiroshima University, Higashi-Hiroshima, Hiroshima, Japan
| | - Takayuki Ookusa
- Department of Biological Science, Graduate School of Science, Hiroshima University, Higashi-Hiroshima, Hiroshima, Japan
| | - Keiju Kamijo
- Department of Anatomy and Anthropology, Graduate School of Medicine, Tohoku University, Sendai, Miyagi, Japan
| | - Kozue Hamao
- Department of Biological Science, Graduate School of Science, Hiroshima University, Higashi-Hiroshima, Hiroshima, Japan
| | - Hiroshi Hosoya
- Department of Biological Science, Graduate School of Science, Hiroshima University, Higashi-Hiroshima, Hiroshima, Japan
- * E-mail:
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20
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5DFRXXL region of long myosin light chain kinase causes F-actin bundle formation. Sci Bull (Beijing) 2013. [DOI: 10.1007/bf03322799] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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21
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Sheykhani R, Shirodkar PV, Forer A. The role of myosin phosphorylation in anaphase chromosome movement. Eur J Cell Biol 2013; 92:175-86. [PMID: 23566798 DOI: 10.1016/j.ejcb.2013.02.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2012] [Revised: 01/26/2013] [Accepted: 02/22/2013] [Indexed: 11/29/2022] Open
Abstract
This work deals with the role of myosin phosphorylation in anaphase chromosome movement. Y27632 and ML7 block two different pathways for phosphorylation of the myosin regulatory light chain (MRLC). Both stopped or slowed chromosome movement when added to anaphase crane-fly spermatocytes. To confirm that the effects of the pharmacological agents were on the presumed targets, we studied cells stained with antibodies against mono- or bi-phosphorylated myosin. For all chromosomes whose movements were affected by a drug, the corresponding spindle fibres of the affected chromosomes had reduced levels of 1P- and 2P-myosin. Thus the drugs acted on the presumed target and myosin phosphorylation is involved in anaphase force production. Calyculin A, an inhibitor of MRLC dephosphorylation, reversed and accelerated the altered movements caused by Y27632 and ML-7, suggesting that another phosphorylation pathway is involved in phosphorylation of spindle myosin. Staurosporine, a more general phosphorylation inhibitor, also reduced the levels of MRLC phosphorylation and caused anaphase chromosomes to stop or slow. The effects of staurosporine on chromosome movements were not reversed by Calyculin A, confirming that another phosphorylation pathway is involved in phosphorylation of spindle myosin.
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Affiliation(s)
- Rozhan Sheykhani
- Department of Biology, York University, Toronto, Ontario M3J 1P3, Canada
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22
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Heissler SM, Manstein DJ. Nonmuscle myosin-2: mix and match. Cell Mol Life Sci 2012; 70:1-21. [PMID: 22565821 PMCID: PMC3535348 DOI: 10.1007/s00018-012-1002-9] [Citation(s) in RCA: 165] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2012] [Revised: 04/16/2012] [Accepted: 04/17/2012] [Indexed: 12/31/2022]
Abstract
Members of the nonmuscle myosin-2 (NM-2) family of actin-based molecular motors catalyze the conversion of chemical energy into directed movement and force thereby acting as central regulatory components of the eukaryotic cytoskeleton. By cyclically interacting with adenosine triphosphate and F-actin, NM-2 isoforms promote cytoskeletal force generation in established cellular processes like cell migration, shape changes, adhesion dynamics, endo- and exo-cytosis, and cytokinesis. Novel functions of the NM-2 family members in autophagy and viral infection are emerging, making NM-2 isoforms regulators of nearly all cellular processes that require the spatiotemporal organization of cytoskeletal scaffolding. Here, we assess current views about the role of NM-2 isoforms in these activities including the tight regulation of NM-2 assembly and activation through phosphorylation and how NM-2-mediated changes in cytoskeletal dynamics and mechanics affect cell physiological functions in health and disease.
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Affiliation(s)
- Sarah M. Heissler
- Institute for Biophysical Chemistry, Hannover Medical School, Carl-Neuberg-Str. 1, 30625 Hannover, Germany
| | - Dietmar J. Manstein
- Institute for Biophysical Chemistry, Hannover Medical School, Carl-Neuberg-Str. 1, 30625 Hannover, Germany
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23
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Kunida K, Matsuda M, Aoki K. FRET imaging and statistical signal processing reveal positive and negative feedback loops regulating the morphology of randomly migrating HT-1080 cells. J Cell Sci 2012; 125:2381-92. [PMID: 22344265 DOI: 10.1242/jcs.096859] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cell migration plays an important role in many physiological processes. Rho GTPases (Rac1, Cdc42, RhoA) and phosphatidylinositols have been extensively studied in directional cell migration. However, it remains unclear how Rho GTPases and phosphatidylinositols regulate random cell migration in space and time. We have attempted to address this issue using fluorescence resonance energy transfer (FRET) imaging and statistical signal processing. First, we acquired time-lapse images of random migration of HT-1080 fibrosarcoma cells expressing FRET biosensors of Rho GTPases and phosphatidyl inositols. We developed an image-processing algorithm to extract FRET values and velocities at the leading edge of migrating cells. Auto- and cross-correlation analysis suggested the involvement of feedback regulations among Rac1, phosphatidyl inositols and membrane protrusions. To verify the feedback regulations, we employed an acute inhibition of the signaling pathway with pharmaceutical inhibitors. The inhibition of actin polymerization decreased Rac1 activity, indicating the presence of positive feedback from actin polymerization to Rac1. Furthermore, treatment with PI3-kinase inhibitor induced an adaptation of Rac1 activity, i.e. a transient reduction of Rac1 activity followed by recovery to the basal level. In silico modeling that reproduced the adaptation predicted the existence of a negative feedback loop from Rac1 to actin polymerization. Finally, we identified MLCK as the probable controlling factor in the negative feedback. These findings quantitatively demonstrate positive and negative feedback loops that involve actin, Rac1 and MLCK, and account for the ordered patterns of membrane dynamics observed in randomly migrating cells.
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Affiliation(s)
- Katsuyuki Kunida
- Department of Pathology and Biology of Diseases, Graduate School of Medicine, Kyoto University, Sakyo-ku, Kyoto, Japan
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24
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Bhuwania R, Cornfine S, Fang Z, Krüger M, Luna EJ, Linder S. Supervillin couples myosin-dependent contractility to podosomes and enables their turnover. J Cell Sci 2012; 125:2300-14. [PMID: 22344260 DOI: 10.1242/jcs.100032] [Citation(s) in RCA: 88] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Podosomes are actin-rich adhesion and invasion structures. Especially in macrophages, podosomes exist in two subpopulations, large precursors at the cell periphery and smaller podosomes (successors) in the cell interior. To date, the mechanisms that differentially regulate these subpopulations are largely unknown. Here, we show that the membrane-associated protein supervillin localizes preferentially to successor podosomes and becomes enriched at precursors immediately before their dissolution. Consistently, podosome numbers are inversely correlated with supervillin protein levels. Using deletion constructs, we find that the myosin II regulatory N-terminus of supervillin [SV(1-174)] is crucial for these effects. Phosphorylated myosin light chain (pMLC) localizes at supervillin-positive podosomes, and time-lapse analyses show that enrichment of GFP-supervillin at podosomes coincides with their coupling to contractile myosin-IIA-positive cables. We also show that supervillin binds only to activated myosin IIA, and a dysregulated N-terminal construct [SV(1-830)] enhances pMLC levels at podosomes. Thus, preferential recruitment of supervillin to podosome subpopulations might both require and induce actomyosin contractility. Using siRNA and pharmacological inhibition, we demonstrate that supervillin and myosin IIA cooperate to regulate podosome lifetime, podosomal matrix degradation and cell polarization. In sum, we show here that podosome subpopulations differ in their molecular composition and identify supervillin, in cooperation with myosin IIA, as a crucial factor in the regulation of podosome turnover and function.
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Affiliation(s)
- Ridhirama Bhuwania
- Institut für Medizinische Mikrobiologie, Virologie und Hygiene, Universitätsklinikum Eppendorf, Hamburg, Germany
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25
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Wang HH, Nakamura A, Yoshiyama S, Ishikawa R, Cai N, Ye LH, Takano-Ohmuro H, Kohama K. Down-Regulation of Myosin Light Chain Kinase Expression in Vascular Smooth Muscle Cells Accelerates Cell Proliferation: Requirement of Its Actin-binding Domain for Reversion to Normal Rates. J Pharmacol Sci 2012; 119:91-6. [DOI: 10.1254/jphs.11213sc] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022] Open
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26
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Skelding KA, Rostas JAP. The role of molecular regulation and targeting in regulating calcium/calmodulin stimulated protein kinases. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 740:703-30. [PMID: 22453966 DOI: 10.1007/978-94-007-2888-2_31] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Calcium/calmodulin-stimulated protein kinases can be classified as one of two types - restricted or multifunctional. This family of kinases contains several structural similarities: all possess a calmodulin binding motif and an autoinhibitory region. In addition, all of the calcium/calmodulin-stimulated protein kinases examined in this chapter are regulated by phosphorylation, which either activates or inhibits their kinase activity. However, as the multifunctional calcium/calmodulin-stimulated protein kinases are ubiquitously expressed, yet regulate a broad range of cellular functions, additional levels of regulation that control these cell-specific functions must exist. These additional layers of control include gene expression, signaling pathways, and expression of binding proteins and molecular targeting. All of the multifunctional calcium/calmodulin-stimulated protein kinases examined in this chapter appear to be regulated by these additional layers of control, however, this does not appear to be the case for the restricted kinases.
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Affiliation(s)
- Kathryn A Skelding
- School of Biomedical Sciences and Pharmacy and Hunter Medical Research Institute, Faculty of Health, The University of Newcastle, University Drive, Callaghan, NSW 2308, Australia
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27
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Leitman EM, Tewari A, Horn M, Urbanski M, Damanakis E, Einheber S, Salzer JL, de Lanerolle P, Melendez-Vasquez CV. MLCK regulates Schwann cell cytoskeletal organization, differentiation and myelination. J Cell Sci 2011; 124:3784-96. [PMID: 22100921 DOI: 10.1242/jcs.080200] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Signaling through cyclic AMP (cAMP) has been implicated in the regulation of Schwann cell (SC) proliferation and differentiation. In quiescent SCs, elevation of cAMP promotes the expression of proteins associated with myelination such as Krox-20 and P0, and downregulation of markers associated with the non-myelinating SC phenotype. We have previously shown that the motor protein myosin II is required for the establishment of normal SC-axon interactions, differentiation and myelination, however, the mechanisms behind these effects are unknown. Here we report that the levels and activity of myosin light chain kinase (MLCK), an enzyme that regulates MLC phosphorylation in non-muscle cells, are dramatically downregulated in SCs after cAMP treatment, in a similar pattern to that of c-Jun, a known inhibitor of myelination. Knockdown of MLCK in SCs mimics the effect of cAMP elevation, inducing plasma membrane expansion and expression of Krox-20 and myelin proteins. Despite activation of myelin gene transcription these cells fail to make compact myelin when placed in contact with axons. Our data indicate that myosin II activity is differentially regulated at various stages during myelination and that in the absence of MLCK the processes of SC differentiation and compact myelin assembly are uncoupled.
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Affiliation(s)
- Ellen M Leitman
- Department of Biological Sciences, Hunter College, City University of New York, New York, NY 10065, USA
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28
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Loss of contraction force in dermal fibroblasts with aging due to decreases in myosin light chain phosphorylation enzymes. Arch Pharm Res 2011; 34:1015-22. [DOI: 10.1007/s12272-011-0619-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2010] [Revised: 12/12/2010] [Accepted: 01/24/2011] [Indexed: 11/25/2022]
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29
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Sit ST, Manser E. Rho GTPases and their role in organizing the actin cytoskeleton. J Cell Sci 2011; 124:679-83. [PMID: 21321325 DOI: 10.1242/jcs.064964] [Citation(s) in RCA: 352] [Impact Index Per Article: 27.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Affiliation(s)
- Soon-Tuck Sit
- sGSK Group, A-Star Neuroscience Research Partnership, Proteos Building, 61 Biopolis Drive, Singapore 138673, Singapore
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30
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Matsumura F, Yamakita Y, Yamashiro S. Myosin light chain kinases and phosphatase in mitosis and cytokinesis. Arch Biochem Biophys 2011; 510:76-82. [PMID: 21396909 PMCID: PMC3114266 DOI: 10.1016/j.abb.2011.03.002] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2010] [Revised: 03/02/2011] [Accepted: 03/03/2011] [Indexed: 01/23/2023]
Abstract
At mitosis, cells undergo drastic alterations in morphology and cytoskeletal organization including cell rounding during prophase, mitotic spindle assembly during prometaphase and metaphase, chromatid segregation in anaphase, and cytokinesis during telophase. It is well established that myosin II is a motor responsible for cytokinesis. Recent reports have indicated that myosin II is also involved in spindle assembly and karyokinesis. In this review, we summarize current understanding of the functions of myosin II in mitosis and cytokinesis of higher eukaryotes, and discuss the roles of possible upstream molecules that control myosin II in these mitotic events.
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Affiliation(s)
- Fumio Matsumura
- Department of Molecular Biology & Biochemistry, Rutgers, Piscataway, NJ 08854, USA.
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31
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Zha J, Chen X, Li C, Zhu M, Ding G, He W. One-Step Construction of Lentiviral Reporter Using Red-Mediated Recombination. Mol Biotechnol 2011; 49:278-82. [DOI: 10.1007/s12033-011-9405-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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32
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Smith TC, Fang Z, Luna EJ. Novel interactors and a role for supervillin in early cytokinesis. Cytoskeleton (Hoboken) 2010; 67:346-64. [PMID: 20309963 DOI: 10.1002/cm.20449] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Supervillin, the largest member of the villin/gelsolin/flightless family, is a peripheral membrane protein that regulates each step of cell motility, including cell spreading. Most known interactors bind within its amino (N)-terminus. We show here that the supervillin carboxy (C)-terminus can be modeled as supervillin-specific loops extending from gelsolin-like repeats plus a villin-like headpiece. We have identified 27 new candidate interactors from yeast two-hybrid screens. The interacting sequences from 12 of these proteins (BUB1, EPLIN/LIMA1, FLNA, HAX1, KIF14, KIFC3, MIF4GD/SLIP1, ODF2/Cenexin, RHAMM, STARD9/KIF16A, Tks5/SH3PXD2A, TNFAIP1) co-localize with and mis-localize EGFP-supervillin in mammalian cells, suggesting associations in vivo. Supervillin-interacting sequences within BUB1, FLNA, HAX1, and MIF4GD also mimic supervillin over-expression by inhibiting cell spreading. Most new interactors have known roles in supervillin-associated processes, e.g. cell motility, membrane trafficking, ERK signaling, and matrix invasion; three (KIF14, KIFC3, STARD9/KIF16A) have kinesin motor domains; and five (EPLIN, KIF14, BUB1, ODF2/cenexin, RHAMM) are important for cell division. GST fusions of the supervillin G2-G3 or G4-G6 repeats co-sediment KIF14 and EPLIN, respectively, consistent with a direct association. Supervillin depletion leads to increased numbers of bi- and multi-nucleated cells. Cytokinesis failure occurs predominately during early cytokinesis. Supervillin localizes with endogenous myosin II and EPLIN in the cleavage furrow, and overlaps with the oncogenic kinesin, KIF14, at the midbody. We conclude that supervillin, like its interactors, is important for efficient cytokinesis. Our results also suggest that supervillin and its interaction partners coordinate actin and microtubule motor functions throughout the cell cycle.
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Affiliation(s)
- Tara C Smith
- Department of Cell Biology and Cell Dynamics Program, University of Massachusetts Medical School, Worcester, Massachusetts, USA
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33
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Wu Q, Sahasrabudhe RM, Luo LZ, Lewis DW, Gollin SM, Saunders WS. Deficiency in myosin light-chain phosphorylation causes cytokinesis failure and multipolarity in cancer cells. Oncogene 2010; 29:4183-93. [PMID: 20498637 PMCID: PMC2911497 DOI: 10.1038/onc.2010.165] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Cancer cells often have unstable genomes and increased centrosome and chromosome numbers, which are an important part of malignant transformation in the most recent model of tumorigenesis. However, very little is known about divisional failures in cancer cells that may lead to chromosomal and centrosomal amplifications. In this study, we show that cancer cells often failed at cytokinesis because of decreased phosphorylation of the myosin regulatory light chain (MLC), a key regulatory component of cortical contraction during division. Reduced MLC phosphorylation was associated with high expression of myosin phosphatase and/or reduced myosin light-chain kinase levels. Furthermore, expression of phosphomimetic MLC largely prevented cytokinesis failure in the tested cancer cells. When myosin light-chain phosphorylation was restored to normal levels by phosphatase knockdown, multinucleation and multipolar mitosis were markedly reduced, resulting in enhanced genome stabilization. Furthermore, both overexpression of myosin phosphatase or inhibition of the myosin light-chain kinase in nonmalignant cells could recapitulate some of the mitotic defects of cancer cells, including multinucleation and multipolar spindles, indicating that these changes are sufficient to reproduce the cytokinesis failures we see in cancer cells. These results for the first time define the molecular defects leading to divisional failure in cancer cells.
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Affiliation(s)
- Q Wu
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA
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34
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Abstract
Cytokinesis is the final step in cell division. The process begins during chromosome segregation, when the ingressing cleavage furrow begins to partition the cytoplasm between the nascent daughter cells. The process is not completed until much later, however, when the final cytoplasmic bridge connecting the two daughter cells is severed. Cytokinesis is a highly ordered process, requiring an intricate interplay between cytoskeletal, chromosomal and cell cycle regulatory pathways. A surprisingly broad range of additional cellular processes are also important for cytokinesis, including protein and membrane trafficking, lipid metabolism, protein synthesis and signaling pathways. As a highly regulated, complex process, it is not surprising that cytokinesis can sometimes fail. Cytokinesis failure leads to both centrosome amplification and production of tetraploid cells, which may set the stage for the development of tumor cells. However, tetraploid cells are abundant components of some normal tissues including liver and heart, indicating that cytokinesis is physiologically regulated. In this chapter, we summarize our current understanding of the mechanisms of cytokinesis, emphasizing steps in the pathway that may be regulated or prone to failure. Our discussion emphasizes findings in vertebrate cells although we have attempted to highlight important contributions from other model systems.
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35
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Jana SS, Kim KY, Mao J, Kawamoto S, Sellers JR, Adelstein RS. An alternatively spliced isoform of non-muscle myosin II-C is not regulated by myosin light chain phosphorylation. J Biol Chem 2009; 284:11563-71. [PMID: 19240025 DOI: 10.1074/jbc.m806574200] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
We report a novel isoform of non-muscle myosin II-C (NM II-C), NM II-C2, that is generated by alternative splicing of an exon, C2, encoding 41 amino acids in mice (33 in humans). The 41 amino acids are inserted into loop 2 of the NM II-C heavy chain within the actin binding region. Unlike most vertebrate non-muscle and smooth muscle myosin IIs, baculovirus-expressed mouse heavy meromyosin (HMM) II-C2 demonstrates no requirement for regulatory myosin light chain (MLC(20)) phosphorylation for maximum actin-activated MgATPase activity or maximum in vitro motility as measured by the sliding actin filament assay. In contrast, noninserted HMM II-C0 and another alternatively spliced isoform HMM II-C1, which contains 8 amino acids inserted into loop 1, are dependent on MLC(20) phosphorylation for both actin-activated MgATPase activity and in vitro motility ( Kim, K. Y., Kovacs, M., Kawamoto, S., Sellers, J. R., and Adelstein, R. S. (2005) J. Biol. Chem. 280, 22769-22775 ). HMM II-C1C2, which contains both the C1 and C2 inserts, does not require MLC(20) phosphorylation for full activity similar to HMM II-C2. These constitutively active C2-inserted isoforms of NM II-C are expressed only in neuronal tissue. This is in contrast to NM II-C1 and NM II-C0, both of which are ubiquitously expressed. Full-length NM II-C2-GFP expressed in COS-7 cells localizes to filaments in interphase cells and to the cytokinetic ring in dividing cells.
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Affiliation(s)
- Siddhartha S Jana
- Laboratory of Molecular Cardiology and Laboratory of Molecular Physiology, NHLBI, National Institutes of Health, Bethesda, Maryland 20892, USA.
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36
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Choi MC, Lee YU, Kim SH, Park JH, Kim HA, Oh DY, Im SA, Kim TY, Jong HS, Bang YJ. A-kinase anchoring protein 12 regulates the completion of cytokinesis. Biochem Biophys Res Commun 2008; 373:85-9. [PMID: 18554502 DOI: 10.1016/j.bbrc.2008.05.184] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2008] [Accepted: 05/30/2008] [Indexed: 10/22/2022]
Abstract
A-kinase anchoring protein 12 (AKAP12) gene is frequently inactivated in human gastric cancer and in several other cancers due to promoter hypermethylation. However, the biological function of AKAP12 in tumorigenesis remains to be identified. Aneuploidy, a hallmark of cancer cells, is often caused by abnormal cell division. In the present study, AKAP12 was found to localize to the cell periphery during interphase and to the actomyosin contractile ring during cytokinesis. Furthermore, AKAP12 depletion using small interfering RNA increased the number of multinucleated cells, and disrupted the completion of cytokinesis. Interestingly, the inhibition of myosin light chain kinase (MLCK), a key regulator of actomyosin contractility, removed AKAP12 from the cell periphery during interphase and from the contractile ring during cytokinesis, suggesting that AKAP12 might be a downstream effector of MLCK. Our findings implicate AKAP12 in the regulation of cytokinesis progression, and suggest a novel role for AKAP12 tumor suppressor.
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Affiliation(s)
- Moon-Chang Choi
- National Research Laboratory for Cancer Epigenetics, Cancer Research Institute, Seoul, Republic of Korea
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37
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Zhang WC, Peng YJ, He WQ, Lv N, Chen C, Zhi G, Chen HQ, Zhu MS. Identification and functional characterization of an aggregation domain in long myosin light chain kinase. FEBS J 2008; 275:2489-500. [PMID: 18400030 DOI: 10.1111/j.1742-4658.2008.06393.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The functions of long smooth muscle myosin light chain kinase (L-MLCK), a molecule with multiple domains, are poorly understood. To examine the existence of further potentially functional domains in this molecule, we analyzed its amino acid sequence with a tango program and found a putative aggregation domain located at the 4Ig domain of the N-terminal extension. To verify its aggregation capability in vitro, expressible truncated L-MLCK variants driven by a cytomegalovirus promoter were transfected into cells. As anticipated, only the overexpression of the 4Ig fragment led to particle formation in Colon26 cells. These particles contained 4Ig polymers and actin. Analysis with detergents demonstrated that the particles shared features in common with aggregates. Thus, we conclude that the 4Ig domain has a potent aggregation ability. To further examine this aggregation domain in vivo, eight transgenic mouse lines expressing the 4Ig domain (4Ig lines) were generated. The results showed that the transgenic mice had typical aggregation in the thigh and diaphragm muscles. Histological examination showed that 7.70 +/- 1.86% of extensor digitorum longus myofibrils displayed aggregates with a 36.44% reduction in myofibril diameter, whereas 65.13 +/- 3.42% of diaphragm myofibrils displayed aggregates and the myofibril diameter was reduced by 43.08%. Electron microscopy examination suggested that the aggregates were deposited at the mitochondria, resulting in structural impairment. As a consequence, the oxygen consumption of mitochondria in the affected muscles was also reduced. Macrophenotypic analysis showed the presence of muscular degeneration characterized by a reduction in force development, faster fatigue, decreased myofibril diameters, and structural alterations. In summary, our study revealed the existence of a novel aggregation domain in L-MLCK and provided a direct link between L-MLCK and aggregation. The possible significance and mechanism underlying the aggregation-based pathological processes mediated by L-MLCK are also discussed.
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38
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Uehara R, Hosoya H, Mabuchi I. In vivo phosphorylation of regulatory light chain of myosin II in sea urchin eggs and its role in controlling myosin localization and function during cytokinesis. ACTA ACUST UNITED AC 2008; 65:100-15. [DOI: 10.1002/cm.20246] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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39
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Chan JY, Takeda M, Briggs LE, Graham ML, Lu JT, Horikoshi N, Weinberg EO, Aoki H, Sato N, Chien KR, Kasahara H. Identification of cardiac-specific myosin light chain kinase. Circ Res 2008; 102:571-80. [PMID: 18202317 DOI: 10.1161/circresaha.107.161687] [Citation(s) in RCA: 118] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Two myosin light chain (MLC) kinase (MLCK) proteins, smooth muscle (encoded by mylk1 gene) and skeletal (encoded by mylk2 gene) MLCK, have been shown to be expressed in mammals. Even though phosphorylation of its putative substrate, MLC2, is recognized as a key regulator of cardiac contraction, a MLCK that is preferentially expressed in cardiac muscle has not yet been identified. In this study, we characterized a new kinase encoded by a gene homologous to mylk1 and -2, named cardiac MLCK, which is specifically expressed in the heart in both atrium and ventricle. In fact, expression of cardiac MLCK is highly regulated by the cardiac homeobox protein Nkx2-5 in neonatal cardiomyocytes. The overall structure of cardiac MLCK protein is conserved with skeletal and smooth muscle MLCK; however, the amino terminus is quite unique, without significant homology to other known proteins, and its catalytic activity does not appear to be regulated by Ca(2+)/calmodulin in vitro. Cardiac MLCK is phosphorylated and the level of phosphorylation is increased by phenylephrine stimulation accompanied by increased level of MLC2v phosphorylation. Both overexpression and knockdown of cardiac MLCK in cultured cardiomyocytes revealed that cardiac MLCK is likely a new regulator of MLC2 phosphorylation, sarcomere organization, and cardiomyocyte contraction.
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Affiliation(s)
- Jason Y Chan
- Department of Physiology and Functional Genomics, University of Florida College of Medicine, 1600 SW Archer Rd, Gainesville, FL 32610-0274, USA
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40
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Matsumura F, Hartshorne DJ. Myosin phosphatase target subunit: Many roles in cell function. Biochem Biophys Res Commun 2007; 369:149-56. [PMID: 18155661 DOI: 10.1016/j.bbrc.2007.12.090] [Citation(s) in RCA: 153] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2007] [Accepted: 12/11/2007] [Indexed: 12/12/2022]
Abstract
Phosphorylation of myosin II is important in many aspects of cell function and involves a myosin kinase, e.g. myosin light chain kinase, and a myosin phosphatase (MP). MP is regulated by the myosin phosphatase target subunit (MYPT1). The domain structure, properties, and genetic analyses of MYPT1 and its isoforms are outlined. MYPT1 binds the catalytic subunit of type 1 phosphatase, delta isoform, and also acts as an interactive platform for many other proteins. A key reaction for MP is with phosphorylated myosin II and the first process shown to be regulated by MP was contractile activity of smooth muscle. In cell division and cell migration myosin II phosphorylation also plays a critical role and these are discussed. However, based on the wide range of partners for MYPT1 it is likely that MP is implicated with substrates other than myosin II. Open questions are whether the diverse functions of MP reflect different cellular locations and/or specific roles for the MYPT1 isoforms.
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Affiliation(s)
- Fumio Matsumura
- Department of Molecular Biology and Biochemistry, Rutgers University, 604, Allison Road, Piscataway, NJ 08855, USA
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41
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Takizawa N, Ikebe R, Ikebe M, Luna EJ. Supervillin slows cell spreading by facilitating myosin II activation at the cell periphery. J Cell Sci 2007; 120:3792-803. [DOI: 10.1242/jcs.008219] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
During cell migration, myosin II modulates adhesion, cell protrusion and actin organization at the leading edge. We show that an F-actin- and membrane-associated scaffolding protein, called supervillin (SV, p205), binds directly to the subfragment 2 domains of nonmuscle myosin IIA and myosin IIB and to the N-terminus of the long form of myosin light chain kinase (L-MLCK). SV inhibits cell spreading via an MLCK- and myosin II-dependent mechanism. Overexpression of SV reduces the rate of cell spreading, and RNAi-mediated knockdown of endogenous SV increases it. Endogenous and EGFP-tagged SV colocalize with, and enhance the formation of, cortical bundles of F-actin and activated myosin II during early cell spreading. The effects of SV are reversed by inhibition of myosin heavy chain (MHC) ATPase (blebbistatin), MLCK (ML-7) or MEK (U0126), but not by inhibiting Rho-kinase with Y-27632. Flag-tagged L-MLCK co-localizes in cortical bundles with EGFP-SV, and kinase-dead L-MLCK disorganizes these bundles. The L-MLCK- and myosin-binding site in SV, SV1-171, rearranges and co-localizes with mono- and di-phosphorylated myosin light chain and with L-MLCK, but not with the short form of MLCK (S-MLCK) or with myosin phosphatase. Thus, the membrane protein SV apparently contributes to myosin II assembly during cell spreading by modulating myosin II regulation by L-MLCK.
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Affiliation(s)
- Norio Takizawa
- Department of Cell Biology, University of Massachusetts Medical School, Worcester, MA 01605, USA
- Cell Dynamics Program, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Reiko Ikebe
- Department of Physiology, University of Massachusetts Medical School, Worcester, MA 01605, USA
- Cell Dynamics Program, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Mitsuo Ikebe
- Department of Physiology, University of Massachusetts Medical School, Worcester, MA 01605, USA
- Cell Dynamics Program, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Elizabeth J. Luna
- Department of Cell Biology, University of Massachusetts Medical School, Worcester, MA 01605, USA
- Cell Dynamics Program, University of Massachusetts Medical School, Worcester, MA 01605, USA
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42
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Zhou M, Wang YL. Distinct pathways for the early recruitment of myosin II and actin to the cytokinetic furrow. Mol Biol Cell 2007; 19:318-26. [PMID: 17959823 DOI: 10.1091/mbc.e07-08-0783] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Equatorial organization of myosin II and actin has been recognized as a universal event in cytokinesis of animal cells. Current models for the formation of equatorial cortex favor either directional cortical transport toward the equator or localized de novo assembly. However, this process has never been analyzed directly in dividing mammalian cells at a high resolution. Here we applied total internal reflection fluorescence microscope (TIRF-M), coupled with spatial temporal image correlation spectroscopy (STICS) and a new analytical approach termed temporal differential microscopy (TDM), to image the dynamics of myosin II and actin during the assembly of equatorial cortex. Our results indicated distinct and at least partially independent mechanisms for the early equatorial recruitment of myosin and actin filaments. Cortical myosin showed no detectable directional flow during early cytokinesis. In addition to equatorial assembly, we showed that localized inhibition of disassembly contributed to the formation of the equatorial myosin band. In contrast to myosin, actin filaments underwent a striking flux toward the equator. Myosin motor activity was required for the actin flux, but not for actin concentration in the furrow, suggesting that there was a flux-independent, de novo mechanism for actin recruitment along the equator. Our results indicate that cytokinesis involves signals that regulate both assembly and disassembly activities and argue against mechanisms that are coupled to global cortical movements.
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Affiliation(s)
- Mian Zhou
- University of Massachusetts Medical School, Department of Physiology, Worcester, MA 01605, USA
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43
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Higginson JR, Thompson O, Winder SJ. Targeting of dystroglycan to the cleavage furrow and midbody in cytokinesis. Int J Biochem Cell Biol 2007; 40:892-900. [PMID: 18054267 DOI: 10.1016/j.biocel.2007.10.019] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2007] [Revised: 10/15/2007] [Accepted: 10/16/2007] [Indexed: 11/28/2022]
Abstract
Dystroglycan is a cell adhesion molecule that interacts with ezrin family proteins and also components of the extracellular signal-regulated kinase pathway. Ezrin and extracellular signal-regulated kinase are both involved in aspects of the cell division cycle. We therefore examined the role of dystroglycan during cytokinesis. Endogenous dystroglycan colocalised with ezrin at the cleavage furrow and midbody during cytokinesis in REF52 cells. Live cell imaging of green fluorescent protein-tagged dystroglycan in Swiss 3T3 and Hela cells revealed a similar localisation. Live cell imaging of a dystroglycan lacking its cytoplasmic domain revealed an even membrane localisation but no cleavage furrow or midbody localisation. Deletion of a previously identified ezrin-binding site in the dystroglycan cytoplasmic domain however only resulted in a slight reduction in cleavage furrow localisation but loss of midbody staining. There was no apparent cytokinetic defect in cells depleted for dystroglycan, however apoptosis levels were considerably higher in dystroglycan knockdown cells. Cell cycle analysis showed a delay in G2/M transition, possibly caused by a more than 50% reduction in extracellular signal-regulated kinase levels in the knockdown cells. Dystroglycan may therefore not only have a role in organising the contractile ring through direct or indirect associations with actin, but can also modulate the cell cycle by affecting extracellular signal-regulated kinase levels.
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Affiliation(s)
- J R Higginson
- Department of Biomedical Science, University of Sheffield, Western Bank, Sheffield S10 2TN, UK
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44
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Batchelder EL, Thomas-Virnig CL, Hardin JD, White JG. Cytokinesis is not controlled by calmodulin or myosin light chain kinase in the Caenorhabditis elegans early embryo. FEBS Lett 2007; 581:4337-41. [PMID: 17716666 PMCID: PMC2144740 DOI: 10.1016/j.febslet.2007.08.005] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2007] [Revised: 07/27/2007] [Accepted: 08/03/2007] [Indexed: 12/16/2022]
Abstract
Furrow ingression in animal cell cytokinesis is controlled by phosphorylation of myosin II regulatory light chain (mRLC). In Caenorhabditis elegans embryos, Rho-dependent Kinase (RhoK) is involved in, but not absolutely required for, this phosphorylation. The calmodulin effector myosin light chain kinase (MLCK) can also phosphorylate mRLC and is widely regarded as a candidate for redundant function with RhoK. However, our results show that RNA mediated interference against C. elegans calmodulin and candidate MLCKs had no effect on cytokinesis in wild-type or RhoK mutant embryos, ruling out the calmodulin/MLCK pathway as the missing regulator of cytokinesis in the C. elegans early embryo.
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Affiliation(s)
- Ellen L Batchelder
- Laboratory of Molecular Biology, University of Wisconsin-Madison, 1525 Linden Drive, Madison, WI 53706, USA
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45
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Ihnatovych I, Hu W, Martin JL, Fazleabas AT, de Lanerolle P, Strakova Z. Increased phosphorylation of myosin light chain prevents in vitro decidualization. Endocrinology 2007; 148:3176-84. [PMID: 17412815 DOI: 10.1210/en.2006-1673] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Differentiation of stromal cells into decidual cells, which is critical to successful pregnancy, represents a complex transformation requiring changes in cytoskeletal architecture. We demonstrate that in vitro differentiation of human uterine fibroblasts into decidual cells includes down-regulation of alpha-smooth muscle actin and beta-tubulin, phosphorylation of focal adhesion kinase, and redistribution of vinculin. This is accompanied by varied adhesion to fibronectin and a modified ability to migrate. Cytoskeletal organization is determined primarily by actin-myosin II interactions governed by the phosphorylation of myosin light chain (MLC20). Decidualization induced by cAMP [with estradiol-17beta (E) and medroxyprogesterone acetate (P)] results in a 40% decrease in MLC20 phosphorylation and a 55% decline in the long (214 kDa) form of myosin light-chain kinase (MLCK). Destabilization of the cytoskeleton by inhibitors of MLCK (ML-7) or myosin II ATPase (blebbistatin) accelerates decidualization induced by cAMP (with E and P) but inhibits decidualization induced by IL-1beta (with E and P). Adenoviral infection of human uterine fibroblast cells with a constitutively active form of MLCK followed by decidualization stimuli leads to a 30% increase in MLC20 phosphorylation and prevents decidualization. These data provide evidence that the regulation of cytoskeletal dynamics by MLC20 phosphorylation is critical for decidualization.
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Affiliation(s)
- Ivanna Ihnatovych
- Department of Obstetrics and Gynecology, The University of Illinois at Chicago, 820 South Wood Street (M/C 808), Chicago, Illinois 60612-7313, USA
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46
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Calloway NT, Choob M, Sanz A, Sheetz MP, Miller LW, Cornish VW. Optimized fluorescent trimethoprim derivatives for in vivo protein labeling. Chembiochem 2007; 8:767-74. [PMID: 17378009 DOI: 10.1002/cbic.200600414] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The combined technologies of optical microscopy and selective probes allow for real-time analysis of protein function in living cells. Synthetic chemistry offers a means to develop specific, protein-targeted probes that exhibit greater optical and chemical functionality than the widely used fluorescent proteins. Here we describe pharmacokinetically optimized, fluorescent trimethoprim (TMP) analogues that can be used to specifically label recombinant proteins fused to E. coli dihydrofolate reductase (eDHFR) in living, wild-type mammalian cells. These improved fluorescent tags exhibited high specificity and fast labeling kinetics, and they could be detected at a high signal-to-noise ratio by using fluorescence microscopy and fluorescence-activated cell sorting (FACS). We also show that fluorescent TMP-eDHFR complexes are complements to green fluorescent protein (GFP) for two-color protein labeling experiments in cells.
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Affiliation(s)
- Nathaniel T Calloway
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA
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47
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Watanabe T, Hosoya H, Yonemura S. Regulation of myosin II dynamics by phosphorylation and dephosphorylation of its light chain in epithelial cells. Mol Biol Cell 2006; 18:605-16. [PMID: 17151359 PMCID: PMC1783795 DOI: 10.1091/mbc.e06-07-0590] [Citation(s) in RCA: 121] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Nonmuscle myosin II, an actin-based motor protein, plays an essential role in actin cytoskeleton organization and cellular motility. Although phosphorylation of its regulatory light chain (MRLC) is known to be involved in myosin II filament assembly and motor activity in vitro, it remains unclear exactly how MRLC phosphorylation regulates myosin II dynamics in vivo. We established clones of Madin Darby canine kidney II epithelial cells expressing MRLC-enhanced green fluorescent protein or its mutants. Time-lapse imaging revealed that both phosphorylation and dephosphorylation are required for proper dynamics of myosin II. Inhibitors affecting myosin phosphorylation and MRLC mutants indicated that monophosphorylation of MRLC is required and sufficient for maintenance of stress fibers. Diphosphorylated MRLC stabilized myosin II filaments and was distributed locally in regions of stress fibers where contraction occurs, suggesting that diphosphorylation is involved in the spatial regulation of myosin II assembly and contraction. We further found that myosin phosphatase or Zipper-interacting protein kinase localizes to stress fibers depending on the activity of myosin II ATPase.
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Affiliation(s)
- Toshiyuki Watanabe
- *RIKEN, Center for Developmental Biology, Kobe 650-0047, Japan
- Department of Life Science, Graduate School of Science and Technology, Kobe University, Kobe 657-8501, Japan; and
| | - Hiroshi Hosoya
- Department of Biological Science, Graduate School of Science, Hiroshima University, Hiroshima, 739-8526, Japan
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Miyauchi K, Yamamoto Y, Kosaka T, Hosoya H. Myosin II activity is not essential for recruitment of myosin II to the furrow in dividing HeLa cells. Biochem Biophys Res Commun 2006; 350:543-8. [PMID: 17022938 DOI: 10.1016/j.bbrc.2006.09.065] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2006] [Accepted: 09/15/2006] [Indexed: 11/21/2022]
Abstract
To elucidate whether phosphorylation of myosin II regulatory light chain (MRLC) is essential for myosin II recruitment to the furrow during cytokinesis, HeLa cells transfected with three types of GFP-tagged recombinant MRLCs, wild-type MRLC, non-phosphorylated form of MRLC, and phosphorylated form of MRLC, were examined. Living cell-imaging showed that both phosphorylated and non-phosphorylated form of MRLCs were recruited to the equator at the same time after anaphase onset, suggesting that phosphorylation of MRLC is not responsible for recruitment of myosin II to the equator. Moreover, the treatment with an inhibitor of myosin II activity, blebbistatin, induced no effect on recruitment of those three recombinant MRLCs. During cytokinesis, phosphorylated but not non-phosphorylated form of MRLC was retained in the equator. These results suggest that phosphorylation of MRLC is essential for retainment of myosin II in the furrow but not for initial recruitment of myosin II to the furrow in dividing HeLa cells.
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Affiliation(s)
- Kenji Miyauchi
- Department of Biological Science, Graduate School of Science, Hiroshima University, Higashi-Hiroshima 739-8526, Japan
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Lucero A, Stack C, Bresnick AR, Shuster CB. A global, myosin light chain kinase-dependent increase in myosin II contractility accompanies the metaphase-anaphase transition in sea urchin eggs. Mol Biol Cell 2006; 17:4093-104. [PMID: 16837551 PMCID: PMC1593176 DOI: 10.1091/mbc.e06-02-0119] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2006] [Revised: 06/15/2006] [Accepted: 07/05/2006] [Indexed: 11/11/2022] Open
Abstract
Myosin II is the force-generating motor for cytokinesis, and although it is accepted that myosin contractility is greatest at the cell equator, the temporal and spatial cues that direct equatorial contractility are not known. Dividing sea urchin eggs were placed under compression to study myosin II-based contractile dynamics, and cells manipulated in this manner underwent an abrupt, global increase in cortical contractility concomitant with the metaphase-anaphase transition, followed by a brief relaxation and the onset of furrowing. Prefurrow cortical contractility both preceded and was independent of astral microtubule elongation, suggesting that the initial activation of myosin II preceded cleavage plane specification. The initial rise in contractility required myosin light chain kinase but not Rho-kinase, but both signaling pathways were required for successful cytokinesis. Last, mobilization of intracellular calcium during metaphase induced a contractile response, suggesting that calcium transients may be partially responsible for the timing of this initial contractile event. Together, these findings suggest that myosin II-based contractility is initiated at the metaphase-anaphase transition by Ca2+-dependent myosin light chain kinase (MLCK) activity and is maintained through cytokinesis by both MLCK- and Rho-dependent signaling. Moreover, the signals that initiate myosin II contractility respond to specific cell cycle transitions independently of the microtubule-dependent cleavage stimulus.
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Affiliation(s)
- Amy Lucero
- Department of Biology, New Mexico State University, Las Cruces, NM 88003, USA
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Yang CX, Chen HQ, Chen C, Yu WP, Zhang WC, Peng YJ, He WQ, Wei DM, Gao X, Zhu MS. Microfilament-binding properties of N-terminal extension of the isoform of smooth muscle long myosin light chain kinase. Cell Res 2006; 16:367-76. [PMID: 16617332 DOI: 10.1038/sj.cr.7310047] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Myosin light chain kinases (MLCK) phosphorylate the regulatory light chain of myosin II in thick filaments and bind to F-actin-containing thin filaments with high affinity. The ability of short myosin light chain kinase (S-MLCK) to bind F-actin is structurally attributed to the DFRXXL regions in its N-terminus. The long myosin light chain kinase (L-MLCK) has two additional DFRXXL motifs and six Ig-like modules in its N-terminal extension. The six Ig-like modules are capable of binding to stress fibers independently. Our results from the imaging analysis demonstrated that the first two intact Ig-like modules (2Ig) in N-terminal extension of L-MLCK is the minimal binding module required for microfilament binding. Binding assay confirmed that F-actin was able to bind 2Ig. Stoichiometries of 2Ig peptide were similar for myofilament or pure F-actin. The binding affinities were slightly lower than 5DFRXXL peptide as reported previously. Similar to DFRXXL peptides, the 2Ig peptide also caused efficient F-actin bundle formation in vitro. In the living cell, over-expression of 2Ig fragment increased "spike"-like protrusion formation with over-bundled F-actin. Our results suggest that L-MLCK may act as a potent F-actin bundling protein via its DFRXXL region and the 2Ig region, implying that L-MLCK plays a role in cytoskeleton organization.
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Affiliation(s)
- Chun Xiang Yang
- Model Animal Research Center and National Key Lab of Medicine, Nanjing University, Nanjing 210061, China
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